In recent years, the method of contactlessly supplying electrical energy to wireless power receivers in a wireless manner has been used instead of the traditional method of supplying electrical energy in a wired manner. The wireless power receiver receiving energy in a wireless manner may be directly driven by the received wireless power, or a battery may be charged by using the received wireless power, then allowing the wireless power receiver to be driven by the charged power.
The Wireless Power Consortium (WPC) which manages technologies for a magnetic inductive wireless power transfer has published a standard document “System description Wireless Power Transfer, Volume 1, Low Power, Part 1: Interface Definition, Version 1.00 Release Candidate 1 (RC1)” for interoperability in the wireless power transfer on Apr. 22, 2010. The standard document of the WPC has described a method of transferring power from one wireless power transmitter to one wireless power receiver by a magnetic induction.
However, a wireless power signal which is generated by one wireless power transmitter to transfer power may be received by a plurality of wireless power receivers. Therefore, there is a need for a method, by which the plurality of wireless power receiver executes communication with the wireless power transmitter to control power transferred.